Role for WNT16B in human epidermal keratinocyte proliferation and differentiation

Class-Wide Analysis of Frizzled-Dishevelled Interactions Using BRET Biosensors Reveals Functional Differences among Receptor Paralogs

Wingless/Int-1 (WNT) signaling is mediated by WNT binding to 10 Frizzleds (FZD1-10), which propagate the signal inside the cell by interacting with different transducers, most prominently the phosphoprotein Dishevelled (DVL). Despite recent progress, questions about WNT/FZD selectivity and paralog-dependent differences in the FZD/DVL interaction remain unanswered. Here, we present a class-wide analysis of the FZD/DVL interaction using the DEP domain of DVL as a proxy in bioluminescence resonance energy transfer (BRET) techniques. Most FZDs engage in a constitutive high-affinity interaction with DEP. Stimulation of unimolecular FZD/DEP BRET sensors with different ligands revealed that most paralogs are dynamic in the FZD/DEP interface, showing distinct profiles in terms of ligand selectivity and signal kinetics. This study underlines mechanistic differences in terms of how allosteric communication between FZDs and their main signal transducer DVL occurs. Moreover, the unimolecular sensors represent the first receptor-focused biosensors to surpass the requirements for high-throughput screening, facilitating FZD-targeted drug discovery.

Studies on Human Cultured Fibroblasts and Cutaneous Squamous Cell Carcinomas Suggest That Overexpression of Histone Variant H2A.J Promotes Radioresistance and Oncogenic Transformation

Background: Cellular senescence in response to ionizing radiation (IR) limits the replication of damaged cells by causing permanent cell cycle arrest. However, IR can induce pro-survival signaling pathways that reduce the extent of radiation-induced cytotoxicity and promote the development of radioresistance. The differential incorporation of histone variant H2A.J has profound effects on higher-order chromatin organization and on establishing the epigenetic state of radiation-induced senescence. However, the precise epigenetic mechanism and function of H2A.J overexpression in response to IR exposure still needs to be elucidated. Methods: Primary (no target, NT) and genetically modified fibroblasts overexpressing H2A.J (H2A.J-OE) were exposed to 20 Gy and analyzed 2 weeks post-IR for radiation-induced senescence by immunohistochemistry and immunofluorescence microscopy. Transcriptome signatures were analyzed in (non-)irradiated NT and H2A.J-OE fibroblasts by RNA sequencing. Since H2A.J plays an important role in the epidermal homeostasis of human skin, the oncogenic potential of H2A.J was investigated in cutaneous squamous cell carcinoma (cSCC). The tissue microarrays of cSCC were analyzed for H2A.J protein expression pattern by automated image analysis. Results: In response to radiation-induced DNA damage, the overexpression of H2A.J impairs the formation of senescence-associated heterochromatin foci (SAHF), thereby inhibiting the SAHF-mediated silencing of proliferation-promoting genes. The dysregulated activation of cyclins and cyclin-dependent kinases disturbs cell cycle arrest in irradiated H2A.J-OE fibroblasts, thereby overcoming radiation-induced senescence. Comparative transcriptome analysis revealed significantly increased WNT16 signaling in H2A.J OE fibroblasts after IR exposure, promoting the fundamental mechanisms of tumor development and progression, including the activation of the epithelial-mesenchymal transition. The quantitative analysis of cSCCs revealed that undifferentiated tumors are associated with high nuclear H2A.J expression, related with greater oncogenic potential. Conclusion: H2A.J overexpression induces radioresistance and promotes oncogenic transformation through the activation of WNT16 signaling pathway functions. H2A.J-associated signatures may improve risk stratification by identifying patients with more aggressive cSCC who may require radiotherapy with increased doses.

Neryl acetate, the major component of Corsican Helichrysum italicum essential oil, mediates its biological activities on skin barrier

Corsican Helichrysum italicum essential oil (HIEO) is characterized by high concentrations of neryl acetate, and we previously demonstrated that Corsican HIEO increases the expression of genes that are part of the differentiation complex (involucrin, small proline rich proteins, late cornified envelope, S100 protein family). The biological activities of HIEO and neryl acetate (NA) were compared to identify how NA contributes to HIEO activity on human skin. NA, as a part component of HIEO, was tested on skin explant models for 24 hours and 5 days in comparison with HIEO. We analyzed the biological regulations in the skin explant by transcriptomic analysis, skin barrier protein immunofluorescence, lipid staining and ceramide analysis by liquid chromatography-mass spectrometry. Transcriptomic analysis revealed that 41.5% of HIEO-modulated genes were also regulated by NA and a selected panel of genes were confirmed by qquantitative reverse transcription PCR analysis. Those genes are involved in epidermal differentiation, skin barrier formation and ceramide synthesis. Involucrin (IVL), involved in formation of the cornified envelope (CE), was upregulated at both gene and protein levels after 24 hours and 5 days respectively. After 5 days of treatment, total lipids and ceramides were also increased. Our results demonstrate that NA mediates a large part of Corsican HIEO activity on skin barrier formation.

WNT16B enhances the proliferation and self-renewal of limbal epithelial cells via CXCR4/MEK/ERK signaling

Culture of limbal epithelial cells (LECs) provides the principal source of transplanted limbal stem cells (LESCs) for treatment of limbal-stem-cell deficiency. Optimization of the culture conditions for in-vitro-expanded LECs will help to create a graft with an optimized quality and quantity of LESCs. This study aimed to investigate the effects of WNT16B on LECs and corneal wound healing and the underlying mechanism. Treatment with exogenous WNT16B increased the proliferative capacity and self-renewal of LECs in the cultures. We further revealed that C-X-C chemokine receptor type 4 (CXCR4) was vital for the effects of WNT16B, and activation of CXCR4/MEK/ERK signaling was pivotal in mediating the effects of WNT16B on LECs enriched for LESCs. The stimulatory effect of WNT16B on corneal epithelial repair was confirmed in a mouse corneal-wound-healing model. In summary, WNT16B enhances proliferation and self-renewal of LECs via the CXCR4/MEK/ERK signaling cascade and accelerates corneal-epithelial wound healing.

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The expression of WNT16B decreases with age

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WNT16B promotes the proliferation and self-renewal of limbal epitheial cells

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The effect of WNT16B on LEC is modulated through CXCR4/MEK/ERK signaling pathway

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WNT16B accelerates corneal-epithelial wound healing

Human limbal epithelial stem cell regulation, bioengineering and function

The corneal epithelium is continuously renewed by limbal stem/progenitor cells (LSCs), a cell population harbored in a highly regulated niche located at the limbus. Dysfunction and/or loss of LSCs and their niche cause limbal stem cell deficiency (LSCD), a disease that is marked by invasion of conjunctival epithelium into the cornea and results in failure of epithelial wound healing. Corneal opacity, pain, loss of vision, and blindness are the consequences of LSCD. Successful treatment of LSCD depends on accurate diagnosis and staging of the disease and requires restoration of functional LSCs and their niche. This review highlights the major advances in the identification of potential LSC biomarkers and components of the LSC niche, understanding of LSC regulation, methods and regulatory standards in bioengineering of LSCs, and diagnosis and staging of LSCD. Overall, this review presents key points for researchers and clinicians alike to consider in deepening the understanding of LSC biology and improving LSCD therapies.

Epigenetic Alterations in Keratinocyte Carcinoma

Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are both derived from epidermal keratinocytes but are phenotypically diverse. To improve the understanding of keratinocyte carcinogenesis, it is critical to understand epigenetic alterations, especially those that govern gene expression. We examined changes to the enhancer-associated histone acetylation mark H3K27ac by mapping matched tumor-normal pairs from 11 patients (five with BCC and six with SCC) undergoing Mohs surgery. Our analysis uncovered cancer-specific enhancers on the basis of differential H3K27ac peaks between matched tumor-normal pairs. We also uncovered biological pathways potentially altered in keratinocyte carcinoma, including enriched epidermal development and Wnt signaling pathways enriched in BCCs and enriched immune response and cell activation pathways in SCCs. We also observed enrichment of transcription factors that implicated SMAD and JDP2 in BCC pathogenesis and FOXP1 in SCC pathogenesis. On the basis of these findings, we prioritized three loci with putative regulation events (FGFR2 enhancer in BCC, intragenic regulation of FOXP1 in SCC, and WNT5A promoter in both subtypes) and validated our findings with published gene expression data. Our findings highlight unique and shared epigenetic alterations in histone modifications and potential regulators for BCCs and SCCs that likely impact the divergent oncogenic pathways, paving the way for targeted drug discoveries.

Expression Profiling and Functional Characterization of miR-26a and miR-130a in Regulating Zhongwei Goat Hair Development via the TGF-β/SMAD Pathway

The Zhongwei goat is an important and unique goat breed indigenous to China. It has a natural hair curling phenotype at birth, but the degree of curling gradually decreases with growth. The molecular mechanism underlying the dynamic changes in the wool curvature in Zhongwei goats is poorly understood. MicroRNAs (miRNAs) play important roles in many biological processes, including hair growth and development. In this study, we selected skins from Zhongwei goats at different ages (45 and 108 days) that exhibited different levels of hair curvature and performed miRNA sequencing to explore the molecular mechanism of hair bending. In total, 28 significantly differentially expressed miRNAs (DE miRNAs) were identified in the three groups of samples between the two developmental stages. An analysis of the target genes of the above-mentioned DE miRNAs by the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses indicated that the DE miRNAs were involved in signal pathways which were previously associated with hair bending and hair follicle development, such as the TGF-β/SMAD, PI3K-Akt, JAK-STAT, and MAPK pathways. A comprehensive analysis of the correlations between the miRNA-seq results and issued transcriptional findings indicated that SMAD1 was a target gene of miR-26a and SMAD5 was a target gene of miR-130a. Furthermore, goat dermal papilla cells were successfully isolated and purified to determine the role of miRNAs in follicle development in vitro. The study results demonstrated that miR-130a and miR-26a had significant effects on the proliferation of dermal papilla cells. In addition, the detection results of mRNA and protein levels indicate that the overexpression of miR-26a can promote the expression of related genes in the TGF-β/SMAD pathway, while miR-130a has the opposite substitution effect. The dual luciferase report test showed that miR-26a targeted the SMAD1 gene and reduced the expression of the SMAD1 protein in hair papillary cells. Our results identified DE microRNAs which perhaps change at the time of hair straightening in Zhongwei goats and explore the role of miR-26a and miR-130a in dermal papilla cells proliferation. The present study provided a theoretical basis to explore the mechanisms underlying the Zhongwei hair growth and curly phenotype.

The effect of extrinsic Wnt/β-catenin signaling in Muller glia on retinal ganglion cell neurite growth

Muller glia are the predominant glial cell type in the retina, and they structurally and metabolically support retinal neurons. Wnt/β-catenin signaling pathways play essential roles in the central nervous system, including glial and neuronal differentiation, axonal growth, and neuronal regeneration. We previously demonstrated that Wnt signaling activation in retinal ganglion cells (RGC) induces axonal regeneration after injury. However, whether Wnt signaling within the adjacent Muller glia plays an axongenic role is not known. In this study, we characterized the effect of Wnt signaling in Muller glia on RGC neurite growth. Primary Muller glia and RGC cells were grown in transwell co-cultures and adenoviral constructs driving Wnt regulatory genes were used to activate and inhibit Wnt signaling specifically in primary Muller glia. Our results demonstrated that activation of Wnt signaling in Muller glia significantly increased RGC average neurite length and branch site number. In addition, the secretome of Muller glia after induction or inhibition of Wnt signaling was characterized using protein profiling of conditioned media by Q Exactive mass spectrometry. The Muller glia secretome after activation of Wnt signaling had distinct and more numerous proteins involved in regulation of axon extension, axon projection and cell adhesion. Furthermore, we showed highly redundant expression of Wnt signaling ligands in Muller glia and Frizzled receptors in RGCs and Muller glia. Therefore, this study provides new information about potential neurite growth promoting molecules in the Muller glia secretome, and identified Wnt-dependent target proteins that may mediate the axonal growth.

The JNK Signaling Pathway in Inflammatory Skin Disorders and Cancer

The c-Jun N-terminal kinases (JNKs), with its members JNK1, JNK2, and JNK3, is a subfamily of (MAPK) mitogen-activated protein kinases. JNK signaling regulates a wide range of cellular processes, including cell proliferation, differentiation, survival, apoptosis, and inflammation. Dysregulation of JNK pathway is associated with a wide range of immune disorders and cancer. Our objective is to provide a review of JNK proteins and their upstream regulators and downstream effector molecules in common skin disorders, including psoriasis, dermal fibrosis, scleroderma, basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and melanoma.

Short Communication: The Association of WNT16 Polymorphisms with the CD4+ T Cell Count in the HIV-Infected Population

WNT16 is one of the 19 members of the human Wnt gene family, and it plays a positive role in lymphocyte proliferation. We investigated the possible association of WNT16 rs3801385 and rs2707466 with the CD4⁺ T cell count among the HIV-infected population in Guangxi, China. A total of 93 HIV-1-infected patients aged 20-75 years were separated into a CD4⁺ T cell count ≥200/mm³ group (60 cases) and a <200/mm³ group (33 cases), and 76 healthy subjects were selected as the control group. All patients have not received any antiretroviral treatment. Direct sequencing was used to detect two functional WNT16 polymorphisms. After adjusting for age and gender, our results showed that rs2707466 A alleles and combined GA+AA genotypes were associated with a CD4⁺ T cell count maintained ≥200/mm³ in the context of HIV infections compared with the control group (odds ratio [OR] = 2.22, 95% confidence interval [CI]: 1.10-4.48, p = .026, and OR = 2.33, 95% CI: 1.03-5.29, p = .044, respectively). When stratified by viral load, this positive association was significantly strengthened in the viral load group of <20 copies/mL. In contrast, there was no significant difference in any genotype and allele of rs3801385 between the patients and healthy controls. In conclusion, the results suggest that the rs2707466 A allele may have a positive effect on maintaining the CD4⁺ T cell count in HIV-infected individuals.

Ras-ERK signalling represses H1.4 phosphorylation at serine 36 to promote non-small-cell lung carcinoma cells growth and migration

Recent papers suggest that oncogenic Ras participate in regulating tumour cells proliferation and metastasis. This work linked Ras with H1.4 modification in non-small-cell lung carcinoma (NSCLC), to better understand the oncogenic effects of Ras. A plasmid for expressing Ras mutated at G13D and T35S was transfected into NCI-H2126 and A549 cells. Phosphorylation of H1.4S36 was determined by immunoblotting. Effects of phosphorylation of H1.4 at serine (S) 36 (H1.4S36ph) on NCI-H2126 and A549 cells were tested by MTT assay, soft-agar colony formation assay, flow cytometry and transwell assay. Chromatin-immunoprecipitation (ChIP) and RT-qPCR were conducted to measure the effects of H1.4S36ph on Ras downstream genes. The catalyzing enzymes participate in H1.4S36 phosphorylation were further studied. We found that Ras-ERK signalling repressed the phosphorylation of H1.4 at S36. H1.4S36ph functioned as a tumour suppressor, as its overexpression repressed NCI-H2126 and A549 cells viability, colony formation, S-phase arrest, migration and invasion. H1.4S36ph was able to mediate the transcription of Ras downstream genes. Ras-ERK signalling repressed H1.4S36ph through degradation of PKA, and the degradation was mediated by MDM2. In conclusion, Ras-ERK signalling repressed H1.4 phosphorylation at S36 to participate in NSCLC cells growth, migration and invasion. Ras-ERK signalling repressed H1.4S36ph through MDM2-dependent degradation of PKA. This study provides a novel explanation for Ras-ERK's tumour-promoting function. Highlights: H1.4S36 phosphorylation is repressed by Ras-ERK activation; H1.4S36ph inhibits the phenotype of NSCLC cells; H1.4S36ph regulates the transcription of Ras downstream genes; Ras-ERK represses H1.4S36ph by MDM2-dependent degradation of PKA.

Hsa_circ_0000479 as a Novel Diagnostic Biomarker of Systemic Lupus Erythematosus

Background: Accumulating evidence suggests that differentially expressed non-coding circular RNAs (circRNAs) play critical roles in the progress of autoimmune diseases. However, the role of circRNAs in systemic lupus erythematosus (SLE) remains unclear. Methods: We initially used next-generation sequencing (NGS) to comprehensively analyze circRNA expression profiles in peripheral blood mononuclear cells (PBMCs) from 10 SLE patients, stratified by their disease activity characteristics (stable or active SLE), and 10 healthy controls (HCs). Candidate circRNAs identified were first validated by quantitative reverse-transcription (qRT)-PCR in PBMC samples from a training-phase cohort of five SLE patients and five HCs. The significantly dysregulated circRNAs were then confirmed by qRT-PCR in a validation cohort of 23 SLE patients and 21 HCs, and in an external validation cohort with 64 SLE patients, 58 HCs, and 50 patients with rheumatoid arthritis (RA). In addition, we conducted bioinformatics analysis and western blotting investigating the relationships between the candidate circRNAs and SLE progression. Results: Multilayer integrative analysis of circRNA regulation showed that 84 circRNAs were upregulated and 30 were downregulated in patients with SLE compared with HCs. We then analyzed the intersection of these differentially expressed circRNAs in an SLE-stable cohort, an SLE-active cohort, and HCs. This enabled us to narrow down dysregulated circRNAs to 15 upregulated circRNAs. Only hsa_circ_0000479 was significantly upregulated in PBMCs of patients with SLE compared with HCs (P < 0.05). Furthermore, the diagnostic potential of hsa_circ_0000479 expression to distinguish SLE patients from HCs and RA patients was also significantly increased in the validation-phase and external-validation-phase cohorts (P < 0.05). When distinguishing SLE patients from HCs, the diagnostic specificities of hsa_circ_0000479 were 0.619 and 1.0 in two validation cohorts, respectively (AUCs = 0.731 and 0.730, respectively). It was also significantly increased in either stable SLE patients or active SLE patients compared with HCs in these two cohorts (P < 0.05). We also used bioinformatics analysis to show that hsa_circ_0000479 regulates SLE progression by modulating metabolic pathways and the Wnt signaling pathway. Western blotting revealed that the expression of Wnt-16 protein was significantly decreased in SLE. Conclusion: Our results suggest that hsa_circ_0000479 has potential as a novel biomarker for the diagnosis of SLE.

Narrowband UVB treatment induces expression of WNT7B, WNT10B and TCF7L2 in psoriasis skin

WNT/β-catenin signaling pathways play a pivotal role in the human immune defense against infections and in chronic inflammatory conditions as psoriasis. Wnt gene alterations are linked to known comorbidities of psoriasis as obesity, diabetes and Crohn’s disease. The objective of this study was to investigate WNT7B, WNT10B, WNT16 and TCF7L2 gene and protein expression in lesional and non-lesional skin and in the peripheral blood of patients with chronic plaque psoriasis compared with healthy individuals. To investigate the effect of narrowband UVB radiation, expression of these genes were analyzed before and after narrowband UVB treatment. Associations between single nucleotide polymorphisms for WNT7B, WNT10B, WNT16 and TCF7L2 genes and psoriasis were tested. Our results show significantly decreased WNT7B, WNT10B and TCF7L2 gene expression in lesional skin compared with non-lesional skin and healthy controls. Narrowband UVB treatment significantly increased expression of these genes in lesional skin. Immunohistochemistry shows increased WNT16 expression in lesional skin. No significant differences in allele or genotype frequencies for Wnt or TCF7L2 gene polymorphisms were found between patient and control group. This study shows for the first time significant UVB induced upregulation of WNT7B, WNT10B and TCF7L2 in patients with psoriasis and suggests a potential role of these genes in psoriasis pathogenesis.

Wnt5a and ROR1 activate non-canonical Wnt signaling via RhoA in TCF3-PBX1 acute lymphoblastic leukemia and highlight new treatment strategies via Bcl-2 co-targeting

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) with TCF3-PBX1 fusion gene expression has constitutively elevated levels of Wnt16b and ROR1 (receptor tyrosine kinase-like orphan receptor), a ligand and a receptor from the Wnt signaling pathway, respectively. Although survival rate is usually high after the initial chemotherapy, many TCF3-PBX1 BCP-ALL patients relapse and subsequently develop treatment resistance, resulting in poor prognosis. Here, we aimed to investigate the molecular signaling associated with Wnt16b and ROR1 overexpression in TCF3-PBX1 cell lines and primary samples, and to identify effective treatment options via ROR1 targeting. We detected higher ROR1 expression on TCF3-PBX1 leukemic cells even at a later stage of patient relapse, providing a strong rationale for the use of ROR1-targeted therapy. We found that Wnt5a-ROR1 signaling enhances proliferation of TCF3-PBX1 cells via RhoA/Rac1 GTPases activation and STAT3 upregulation. Wnt16b also activated the RhoA/Rac1 signaling cascade suggesting the activation of a non-canonical Wnt pathway in TCF3-PBX1 cells. Wnt16 could interact with ROR1 but not in TCF3-PBX1 cells, suggesting that Wnt5a is the ligand signaling via ROR1 in TCF3-PBX1 cells. By high throughput drug-sensitivity testing of TCF3-PBX1 cells before and after ROR1 knockdown we found that targeting ROR1 significantly improves the therapeutic efficacy of Bcl-2 family inhibitors venetoclax and navitoclax, and this synergism was confirmed ex vivo using a drug-resistant primary sample from a relapsed TCF3-PBX1 patient. Our work underlines a new type of targeted combination therapy that could be clinically advantageous for patients with TCF3-PBX1 BCP-ALL.

Ras-ERK1/2 signaling contributes to the development of colorectal cancer via regulating H3K9ac

BACKGROUNDS/AIMS

Ras is a control switch of ERK1/2 pathway, and hyperactivation of Ras-ERK1/2 signaling appears frequently in human cancers. However, the molecular regulation following by Ras-ERK1/2 activation is still unclear. This work aimed to reveal whether Ras-ERK1/2 promoted the development of colorectal cancer via regulating H3K9ac.

METHODS

A vector for expression of K-Ras mutated at G12 V and T35S was transfected into SW48 cells, and the acetylation of H3K9 was measured by Western blot analysis. MTT assay, colony formation assay, transwell assay, chromatin immunoprecipitation and RT-qPCR were performed to detect whether H3K9ac was contributed to K-Ras-mediated cell growth and migration. Furthermore, whether HDAC2 and PCAF involved in modification of H3K9ac following Ras-ERK1/2 activation were studied.

RESULTS

K-Ras mutated at G12 V and T35S induced a significant activation of ERK1/2 signaling and a significant down-regulation of H3K9ac. Recovering H3K9 acetylation by using a mimicked H3K9ac expression vector attenuated the promoting effects of Ras-ERK1/2 on tumor cells growth and migration. Besides, H3K9ac can be deacetylated by HDAC2 and MDM2-depedent degradation of PCAF.

CONCLUSION

H3K9ac was a specific target for Ras-ERK1/2 signaling pathway. H3K9 acetylation can be modulated by HDAC2 and MDM2-depedent degradation of PCAF. The revealed regulation provides a better understanding of Ras-ERK1/2 signaling in tumorigenesis.

High-throughput sequencing of hair follicle development-related micrornas in cashmere goat at various fetal periods

Inner Mongolia cashmere goat marks a precious gerplasm genetic resource due to its excellent cashmere traits. Therefore, it is of crucial importance to investigate the cashmere development mechanism of cashmere goat and to search for the important cashmere growth-related candidate genes. Fetal skin samples at 10 different periods of cashmere goat were collected in this research. Moreover, high-throughput sequencing was conducted on RNA samples from side skin of cashmere goat fetuses collected at three critical periods of skin hair follicle initiation, growth and development (namely, 45, 55 and 65 days) after balanced mix in line with the previous research results. Meanwhile, 3 samples at corresponding periods were used as the biological duplications. Data regarding microRNA and mRNA expression in skin and hair follicles of cashmere goats at various fetal periods were obtained using the high-throughput sequencing method. The results indicated that microRNAs in the oar-let-7 and oar-miR-200 families in 55 days and 66 days of pregnancy samples had been notably up-regulated relative to those in 45 days of pregnancy samples. This revealed that they might be the critical microRNAs in hair follicle development.

Mechanisms of Wnt signaling and control

The Wnt signaling pathway is a highly conserved system that regulates complex biological processes across all metazoan species. At the cellular level, secreted Wnt proteins serve to break symmetry and provide cells with positional information that is critical to the patterning of the entire body plan. At the organismal level, Wnt signals are employed to orchestrate fundamental developmental processes, including the specification of the anterior-posterior body axis, induction of the primitive streak and ensuing gastrulation movements, and the generation of cell and tissue diversity. Wnt functions extend into adulthood where they regulate stem cell behavior, tissue homeostasis, and damage repair. Disruption of Wnt signaling activity during embryonic development or in adults results in a spectrum of abnormalities and diseases, including cancer. The molecular mechanisms that underlie the myriad of Wnt-regulated biological effects have been the subject of intense research for over three decades. This review is intended to summarize our current understanding of how Wnt signals are generated and interpreted. This article is categorized under: Biological Mechanisms > Cell Signaling Developmental Biology > Stem Cell Biology and Regeneration.

Mutations, Differential Gene Expression, and Chimeric Transcripts in Esophageal Squamous Cell Carcinoma Show High Heterogeneity

Esophageal squamous cell carcinoma (ESCC) is a frequent and lethal neoplasia. As recent advances in targeted therapy have not improved ESCC prognosis, characterization of molecular alterations associated to this tumor is of foremost relevance. In this study, we analyze, for the first time, the complete genomic profile of ESCC by RNA-seq. TP53 was the most frequently mutated gene in the investigation and validation sets (78.6% and 67.4%, respectively). Differential expression analysis between tumor and nontumor adjacent mucosa showed 6698 differentially expressed genes, most of which were overexpressed (74%). Enrichment analysis identified overrepresentation of Wnt pathway, with overexpressed activators and underexpressed inactivators, suggesting activation of canonical and noncanonical Wnt signaling pathways. Higher WNT7B expression was associated with poor prognosis. Twenty-one gene fusions were identified in 50% of tumors, none of which involving the same genes in different patients; 71% of fusions involved syntenic genes. Comparisons with TCGA data showed co-amplification of seven gene pairs involved in fusions in the present study (~33%), suggesting that these rearrangements might have been driven by chromoanagenesis. In conclusion, genomic alterations in ESCC are highly heterogeneous, impacting negatively in target therapy development.

Global gene expression analysis identifies Mef2c as a potential player in Wnt16-mediated transcriptional regulation

Wnt16 is a major Wnt ligand involved in the regulation of postnatal bone homeostasis. Previous studies have shown that Wnt16 promotes bone formation and inhibits bone resorption, suggesting that this molecule could be targeted for therapeutic interventions to treat bone thinning disorders such as osteoporosis. However, the molecular mechanisms by which Wnt16 regulates bone metabolism is not yet fully understood. To better understand the molecular mechanisms by which Wnt16 promotes bone formation and to identify the target genes regulated by Wnt16 in osteoblasts, we treated calvarial osteoblasts purified from C57Bl/6 mice with recombinant Wnt16 and profiled the gene expression changes by RNA-seq at 24 h post-treatment. We also compared gene expression profiles of Wnt16-treated osteoblasts to canonical Wnt3a- and non-canonical Wnt5a-treated osteoblasts. This study identified 576 genes differentially expressed in Wnt16-treated osteoblasts compared to sham-treated controls; these included several members of Wnt pathway (Wnt2b, Wnt7b, Wnt11, Axin2, Sfrp2, Sfrp4, Fzd5 etc.) and TGF-β/BMP signaling pathway (Bmp7, Inhba, Inhbb, Tgfb2 etc.). Wnt16 also regulated a large number of genes with known bone phenotypes. We also found that about 37% (215/576) of the Wnt16 targets overlapped with Wnt3a targets and ~15% (86/576) overlapped with Wnt5a targets, suggesting that Wnt16 activates both canonical and non-canonical Wnt signaling targets in osteoblasts. Transcription factor binding motif enrichment analysis in the promoter regions of Wnt16 targets identified noncanonical Wnt/JNK pathway activated transcription factors Fosl2 and Fosl1 as two of the most significantly enriched transcription factors associated with genes activated by Wnt16 while Mef2c was the most significantly enriched transcription factor associated with genes repressed by Wnt16. We also found that a large number of Mef2c targets overlapped with genes down-regulated by Wnt16 and Mef2c itself was transcriptionally repressed by Wnt16 suggesting that Mef2c plays a role in Wnt16-mediated transcriptional regulation.

Epidermal YAP activity drives canonical WNT16/β-catenin signaling to promote keratinocyte proliferation in vitro and in the murine skin

The skin constantly self-renews throughout adult life. Wnt/β-catenin signaling plays a key role in promoting keratinocyte proliferation in the hair follicles and in the interfollicular epidermis. A recent report demonstrated that epidermal YAP activity drives β-catenin activation to promote keratinocyte proliferation in the murine skin. However, it remains unclear whether this is caused by paracrine activation of canonical Wnt signaling or through other YAP/β-catenin regulatory interactions. In the present study, we found that XAV939-inhibition of canonical WNT signaling in skin of YAP2-5SA-ΔC mice resulted in diminished β-catenin activation, reduced keratinocyte proliferation, and a mitigation of the hyperplastic abnormalities in the interfollicular epidermis, signifying a canonical WNT ligand-dependent mechanism. Our subsequent analyses determined that WNT16 is produced in response to YAP activity in keratinocytes both in vitro and in vivo, and that WNT16 drives HaCaT keratinocyte proliferation via canonical WNT16/β-catenin signaling. We conclude that under normal physiological conditions WNT16 is the paracrine WNT ligand secreted in response to epidermal YAP activity that promotes cell proliferation in the interfollicular epidermis. This study delineates a fundamental YAP-driven mechanism that controls normal skin regeneration, and that may be perturbed in human regenerative disease displaying increased YAP and WNT signaling activity.

Glucocorticoids, genes and brain function

The identification of key genes in transcriptomic data constitutes a huge challenge. Our review of microarray reports revealed 88 genes whose transcription is consistently regulated by glucocorticoids (GCs), such as cortisol, corticosterone and dexamethasone, in the brain. Replicable transcriptomic data were combined with biochemical and physiological data to create an integrated view of the effects induced by GCs. The most frequently reported genes were Errfi1 and Ddit4. Their up-regulation was associated with the altered transcription of genes regulating growth factor and mTORC1 signaling (Gab1, Tsc22d3, Dusp1, Ndrg2, Ppp5c and Sesn1) and progression of the cell cycle (Ccnd1, Cdkn1a and Cables1). The GC-induced reprogramming of cell function involves changes in the mRNA level of genes responsible for the regulation of transcription (Klf9, Bcl6, Klf15, Tle3, Cxxc5, Litaf, Tle4, Jun, Sox4, Sox2, Sox9, Irf1, Sall2, Nfkbia and Id1) and the selective degradation of mRNA (Tob2). Other genes are involved in the regulation of metabolism (Gpd1, Aldoc and Pdk4), actin cytoskeleton (Myh2, Nedd9, Mical2, Rhou, Arl4d, Osbpl3, Arhgef3, Sdc4, Rdx, Wipf3, Chst1 and Hepacam), autophagy (Eva1a and Plekhf1), vesicular transport (Rhob, Ehd3, Vps37b and Scamp2), gap junctions (Gjb6), immune response (Tiparp, Mertk, Lyve1 and Il6r), signaling mediated by thyroid hormones (Thra and Sult1a1), calcium (Calm2), adrenaline/noradrenaline (Adcy9 and Adra1d), neuropeptide Y (Npy1r) and histamine (Hdc). GCs also affected genes involved in the synthesis of polyamines (Azin1) and taurine (Cdo1). The actions of GCs are restrained by feedback mechanisms depending on the transcription of Sgk1, Fkbp5 and Nr3c1. A side effect induced by GCs is increased production of reactive oxygen species. Available data show that the brain's response to GCs is part of an emergency mode characterized by inactivation of non-core activities, restrained inflammation, restriction of investments (growth), improved efficiency of energy production and the removal of unnecessary or malfunctioning cellular components to conserve energy and maintain nutrient supply during the stress response.

Serum bone-turnover biomarkers are associated with the occurrence of peripheral and axial arthritis in psoriatic disease: a prospective cross-sectional comparative study

Background

A recent systematic review identified four candidate serum-soluble bone-turnover biomarkers (dickkopf-1, Dkk-1; macrophage-colony stimulating factor, M-CSF; matrix metalloproteinase-3, MMP-3; osteoprotegerin, OPG) showing possible association with psoriatic arthritis (PsA). We aimed to: (i) confirm and determine if these four biomarkers are associated with PsA; (ii) differentiate psoriasis cases with and without arthritis; and (iii) differentiate PsA cases with and without axial arthritis.

Methods

A prospective cross-sectional comparative two-centre study recruited 200 patients with psoriasis without arthritis (PsC), 127 with PsA without axial arthritis (pPsA), 117 with PsA with axial arthritis (psoriatic spondyloarthritis, PsSpA), 157 with ankylosing spondylitis (AS) without psoriasis, and 50 matched healthy controls (HC). Serum biomarker concentrations were measured using ELISA. Multivariable regression and receiver operating characteristic analyses were performed.

Results

MMP-3 concentrations were significantly higher and M-CSF significantly lower in each arthritis disease group compared with HC (p ≤ 0.02). MMP-3 concentrations were significantly higher (adjusted odds ratio, OR_adj 1.02 per ng/ml increase in concentration; p = 0.0004) and M-CSF significantly lower (OR_adj 0.44 per ng/ml increase; p = 0.01) in PsA (pPsA and PsSpA combined) compared with PsC. Dkk-1 concentrations were significantly higher (OR_adj 1.22 per ng/mL increase; p = 0.01), and OPG concentrations significantly lower (OR_adj 0.20 per ng/mL increase; p = 0.02) in patients with axial arthritis (PsSpA and AS combined) than in those without (pPsA). Furthermore, Dkk-1 concentrations were significantly higher along a spectrum of increasing axial arthritis; Dkk-1 concentrations were higher in AS compared with PsSpA (OR_adj 1.18 per ng/mL increase; p = 0.02). Receiver operating characteristic analysis showed MMP-3 to be the best single biomarker for differentiating PsA from PsC (AUC 0.70 for a cut-off of 14.51 ng/mL; sensitivity 0.76, specificity 0.60).

Conclusions

MMP-3 and M-CSF are biomarkers for the presence of arthritis in psoriatic disease, and could therefore be used to screen for PsA in psoriasis cohorts. Dkk-1 and OPG are biomarkers of axial arthritis; they could therefore be used to screen for the presence of axial disease in PsA cases, and help differentiate PsSpA from AS. High concentrations of Dkk-1 in AS and PsSpA compared with HC, support previous reports that Dkk-1 is dysfunctional in the spondyloarthritides.

Expression of low-density lipoprotein-related receptors 5 and 6 (LRP5/6) in psoriasis skin

Low-density lipoprotein-related receptors 5 and 6 (LRP5/6) are transmembrane receptors with key functions in canonical Wnt signalling. Wnt ligands are thought to play an important role in innate immunity and psoriasis, and recent studies assigned LRP5/6 anti-inflammatory properties. The objective of this study was to investigate the expression of LRP5 and LRP6 in lesional and non-lesional skin in peripheral blood and in mononuclear cells of patients with chronic plaque type psoriasis compared with control individuals. To investigate the effect of UV-B radiation, LRP5/6 skin gene expression was analysed before and after narrowband UV-B treatment. Our results showed significantly decreased gene expression of LRP5 and LRP6 in lesional skin and in peripheral blood from patients with psoriasis compared with non-lesional skin and healthy control skin. Immunohistochemistry did not reveal differences in protein expression of LRP5/6. Narrowband UV-B treatment induced a significant increase in LRP5 and LRP6 gene expression in lesional skin. Decreased gene expression of LRP5/6 in lesional skin and upregulation after nb UV-B treatment suggest a possible role for LRP5/6 in psoriasis.

Wnt signalling controls the response to mechanical loading during zebrafish joint development

Joint morphogenesis requires mechanical activity during development. Loss of mechanical strain causes abnormal joint development, which can impact long-term joint health. Although cell orientation and proliferation are known to shape the joint, dynamic imaging of developing joints in vivo has not been possible in other species. Using genetic labelling techniques in zebrafish we were able, for the first time, to dynamically track cell behaviours in intact moving joints. We identify that proliferation and migration, which contribute to joint morphogenesis, are mechanically controlled and are significantly reduced in immobilised larvae. By comparison with strain maps of the developing skeleton, we identify canonical Wnt signalling as a candidate for transducing mechanical forces into joint cell behaviours. We show that, in the jaw, Wnt signalling is reduced specifically in regions of high strain in response to loss of muscle activity. By pharmacological manipulation of canonical Wnt signalling, we demonstrate that Wnt acts downstream of mechanical activity and is required for joint patterning and chondrocyte maturation. Wnt16, which is also downstream of muscle activity, controls proliferation and migration, but plays no role in chondrocyte intercalation.

GLI2 Is a Regulator of β-Catenin and Is Associated with Loss of E-Cadherin, Cell Invasiveness, and Long-Term Epidermal Regeneration

Uncontrolled hedgehog (HH)/glioma-associated oncogene (GLI) and WNT/β-catenin signaling are important events in the genesis of many cancers including skin cancer and are often implicated in tumor progression, invasion, and metastasis. However, because of the complexity and context dependency of both pathways, little is known about HH and WNT interactions in human carcinogenesis. In the current study, we provide evidence of HH/glioma-associated oncogene family zinc finger 2 (GLI2)-WNT/β-catenin signaling crosstalk in human keratinocytes. Overexpression of GLI2ΔN in human keratinocytes resulted in cytoplasmic accumulation and nuclear relocalization of β-catenin in vitro and in 3D organotypic cultures, accompanied by upregulation of WNT genes. Induction of GLI2ΔN enhanced the β-catenin-dependent transcriptional activation and the subsequent activation of β-catenin target genes including cyclin-D1. Additionally, GLI2 overexpression was associated with decreased E-cadherin protein levels; increased expression of SNAIL, matrix metalloproteinase 2, and integrin β1; and increased cell invasion in 3D organotypic cultures. Invasion was reduced by WNT inhibition, thus unveiling the direct role of GLI2/WNT crosstalk in cell invasion. We show that GLI2 overexpression supported long-term epidermal regeneration in 3D organotypic cultures, and resulted in the manifestation of an undifferentiated basal/stem cell-associated phenotype in human keratinocytes. Both these observations are consistent with the role of β-catenin and SNAIL in epidermal stem cell maintenance. This work suggests that GLI2 is a regulator of β-catenin and provides insights into its role in tumorigenesis.

Alternative splicing within the Wnt signaling pathway: role in cancer development

BACKGROUND

The Wnt signaling cascade plays a fundamental role in embryonic development, adult tissue regeneration, homeostasis and stem cell maintenance. Abnormal Wnt signaling has been found to be prevalent in various human cancers. Also, a role of Wnt signaling in the regulation of alternative splicing of several cancer-related genes has been established. In addition, accumulating evidence suggests the existence of multiple splice isoforms of Wnt signaling cascade components, including Wnt ligands, receptors, components of the destruction complex and transcription activators/suppressors. The presence of multiple Wnt signaling-related isoforms may affect the functionality of the Wnt pathway, including its deregulation in cancer. As such, specific Wnt pathway isoform components may serve as therapeutic targets or as biomarkers for certain human cancers. Here, we review the role of alternative splicing of Wnt signaling components during the onset and progression of cancer.

CONCLUSIONS

Splice isoforms of components of the Wnt signaling pathway play distinct roles in cancer development. Isoforms of the same component may function in a tissue- and/or cancer-specific manner. Splice isoform expression analyses along with deregulated Wnt signaling pathway analyses may be of help to design efficient diagnostic and therapeutic strategies.

microRNA regulation of Wnt signaling pathways in development and disease

Wnt signaling pathways and microRNAs (miRNAs) are critical regulators of development. Aberrant Wnt signaling pathways and miRNA levels lead to developmental defects and diverse human pathologies including but not limited to cancer. Wnt signaling pathways regulate a plethora of cellular processes during embryonic development and maintain homeostasis of adult tissues. A majority of Wnt signaling components are regulated by miRNAs which are small noncoding RNAs that are expressed in both animals and plants. In animal cells, miRNAs fine tune gene expression by pairing primarily to the 3'untranslated region of protein coding mRNAs to repress target mRNA translation and/or induce target degradation. miRNA-mediated regulation of signaling transduction pathways is important in modulating dose-sensitive response of cells to signaling molecules. This review discusses components of the Wnt signaling pathways that are regulated by miRNAs in the context of development and diseases. A fundamental understanding of miRNA functions in Wnt signaling transduction pathways may yield new insight into crosstalks of regulatory mechanisms essential for development and disease pathophysiology leading to novel therapeutics.

A new WNT on the bone: WNT16, cortical bone thickness, porosity and fractures

The last decade has provided abundant data implicating the WNT pathway in bone development and in the regulation of skeletal homeostasis. Rare human mutations together with gain- and loss-of-function approaches in mice have clearly demonstrated that disrupted regulation of this pathway leads to altered bone mass. In addition to these rare human and mice mutations, large population-based genome-wide association studies (GWASs) have identified single-nucleotide polymorphisms in ∼60 loci strongly associated with variations in bone mineral density (BMD) at different skeletal sites. Among the loci/genes identified by BMD GWAS, components of the WNT signaling pathway are numerous and have been shown to contribute to skeletal development and homeostasis. Within the components of WNT signaling, the gene coding for WNT16, one of the 19 WNT ligands of the human genome, has been found strongly associated with specific bone traits such as cortical bone thickness, cortical porosity and fracture risk. Recently, the first functional characterization of Wnt16 has confirmed the critical role of Wnt16 in the regulation of cortical bone mass and bone strength in mice. These reports have extended our understanding of Wnt16 function in bone homeostasis and have not only confirmed the unique association of Wnt16 with cortical bone and fracture susceptibility, as suggested by GWAS in human populations, but have also provided novel insights into the biology of this WNT ligand and the mechanism(s) by which it regulates cortical but not trabecular bone homeostasis. Most interestingly, Wnt16 appears to be a strong anti-resorptive soluble factor acting on both osteoblasts and osteoclast precursors.

Wnt16 attenuates TGFβ-induced chondrogenic transformation in vascular smooth muscle

OBJECTIVE

Phenotypic plasticity of vascular smooth muscle cells (VSMCs) contributes to cardiovascular disease. Chondrocyte-like transformation of VSMCs associates with vascular calcification and underlies the formation of aortic cartilaginous metaplasia induced in mice by genetic loss of matrix Gla protein (MGP). Previous microarray analysis identified a dramatic downregulation of Wnt16 in calcified MGP-null aortae, suggesting an antagonistic role for Wnt16 in the chondrogenic transformation of VSMCs.

APPROACH AND RESULTS

Wnt16 is significantly downregulated in MGP-null aortae, before the histological appearance of cartilaginous metaplasia, and in primary MGP-null VSMCs. In contrast, intrinsic TGFβ is activated in MGP-null VSMCs and is necessary for spontaneous chondrogenesis of these cells in high-density micromass cultures. TGFβ3-induced chondrogenic transformation in wild-type VSMCs associates with Smad2/3-dependent Wnt16 downregulation, but Wnt16 does not suppress TGFβ3-induced Smad activation. In addition, TGFβ3 inhibits Notch signaling in wild-type VSMCs, and this pathway is downregulated in MGP-null aortae. Exogenous Wnt16 stimulates Notch activity and attenuates TGFβ3-induced downregulation of Notch in wild-type VSMCs, prevents chondrogenesis in MGP-null and TGFβ3-treated wild-type VSMCs, and stabilizes expression of contractile markers of differentiated VSMCs.

CONCLUSIONS

We describe a novel TGFβ-Wnt16-Notch signaling conduit in the chondrocyte-like transformation of VSMCs and identify endogenous TGFβ activity in MGP-null VSMCs as a critical mediator of chondrogenesis. Our proposed model suggests that the activated TGFβ pathway inhibits expression of Wnt16, which is a positive regulator of Notch signaling and a stabilizer of VSMC phenotype. These data advance the comprehensive mechanistic understanding of VSMC transformation and may identify a novel potential therapeutic target in vascular calcification.

Role of WNT16 in the regulation of periosteal bone formation in female mice

In this study, we evaluated the role of WNT16 in regulating bone size, an important determinant of bone strength. Mice with targeted disruption of the Wnt16 gene exhibited a 24% reduction in tibia cross-sectional area at 12 weeks of age compared with that of littermate wild-type (WT) mice. Histomorphometric studies revealed that the periosteal bone formation rate and mineral apposition rate were reduced (P < .05) by 55% and 32%, respectively, in Wnt16 knockout (KO) vs WT mice at 12 weeks of age. In contrast, the periosteal tartrate resistant acid phosphatase-labeled surface was increased by 20% in the KO mice. Because mechanical strain is an important physiological regulator of periosteal bone formation (BF), we determined whether mechanical loading-induced periosteal BF is compromised in Wnt16 KO mice. Application of 4800-μe strain to the right tibia using a 4-point bending loading method for 2 weeks (2-Hz frequency, 36 cycles per day, 6 days/wk) produced a significant increase in cross-sectional area (11% above that of the unloaded left tibia, P < .05, n = 6) in the WT but not in the KO mice (-0.2% change). Histomorphometric analyses revealed increases in the periosteal bone formation rate and mineral apposition rate in the loaded bones of WT but not KO mice. Wnt16 KO mice showed significant (20%-70%) reductions in the expression levels of markers of canonical (β-catenin and Axin2) but not noncanonical (Nfatc1 and Tnnt2) WNT signaling in the periosteum at 5 weeks of age. Our findings suggest that WNT16 acting via canonical WNT signaling regulates mechanical strain-induced periosteal BF and bone size.

Osteoblast-derived WNT16 represses osteoclastogenesis and prevents cortical bone fragility fractures

The WNT16 locus is a major determinant of cortical bone thickness and nonvertebral fracture risk in humans. The disability, mortality and costs caused by osteoporosis-induced nonvertebral fractures are enormous. We demonstrate here that Wnt16-deficient mice develop spontaneous fractures as a result of low cortical thickness and high cortical porosity. In contrast, trabecular bone volume is not altered in these mice. Mechanistic studies revealed that WNT16 is osteoblast derived and inhibits human and mouse osteoclastogenesis both directly by acting on osteoclast progenitors and indirectly by increasing expression of osteoprotegerin (Opg) in osteoblasts. The signaling pathway activated by WNT16 in osteoclast progenitors is noncanonical, whereas the pathway activated in osteoblasts is both canonical and noncanonical. Conditional Wnt16 inactivation revealed that osteoblast-lineage cells are the principal source of WNT16, and its targeted deletion in osteoblasts increases fracture susceptibility. Thus, osteoblast-derived WNT16 is a previously unreported key regulator of osteoclastogenesis and fracture susceptibility. These findings open new avenues for the specific prevention or treatment of nonvertebral fractures, a substantial unmet medical need.

Intersection of AHR and Wnt signaling in development, health, and disease

The AHR (aryl hydrocarbon receptor) and Wnt (wingless-related MMTV integration site) signaling pathways have been conserved throughout evolution. Appropriately regulated signaling through each pathway is necessary for normal development and health, while dysregulation can lead to developmental defects and disease. Though both pathways have been vigorously studied, there is relatively little research exploring the possibility of crosstalk between these pathways. In this review, we provide a brief background on (1) the roles of both AHR and Wnt signaling in development and disease, and (2) the molecular mechanisms that characterize activation of each pathway. We also discuss the need for careful and complete experimental evaluation of each pathway and describe existing research that explores the intersection of AHR and Wnt signaling. Lastly, to illustrate in detail the intersection of AHR and Wnt signaling, we summarize our recent findings which show that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-induced disruption of Wnt signaling impairs fetal prostate development.

MAL overexpression leads to disturbed expression of genes that influence cytoskeletal organization and differentiation of Schwann cells

In the developing peripheral nervous system, a coordinated reciprocal signaling between Schwann cells and axons is crucial for accurate myelination. The myelin and lymphocyte protein MAL is a component of lipid rafts that is important for targeting proteins and lipids to distinct domains. MAL overexpression impedes peripheral myelinogenesis, which is evident by a delayed onset of myelination and reduced expression of the myelin protein zero (Mpz/P0) and the low-affinity neurotrophin receptor p75(NTR). This study shows that MAL overexpression leads to a significant reduction of Mpz and p75(NTR) expression in primary mouse Schwann cell cultures, which was already evident before differentiation, implicating an effect of MAL in early Schwann cell development. Their transcription was robustly reduced, despite normal expression of essential transcription factors and receptors. Further, the cAMP response element-binding protein (CREB) and phosphoinositide 3-kinase signaling pathways important for Schwann cell differentiation were correctly induced, highlighting that other so far unknown rate limiting factors do exist. We identified novel genes expressed by Schwann cells in a MAL-dependent manner in vivo and in vitro. A number of those, including S100a4, RhoU and Krt23, are implicated in cytoskeletal organization and plasma membrane dynamics. We showed that S100a4 is predominantly expressed by nonmyelinating Schwann cells, whereas RhoU was localized within myelin membranes, and Krt23 was detected in nonmyelinating as well as in myelinating Schwann cells. Their differential expression during early peripheral nerve development further underlines their possible role in influencing Schwann cell differentiation and myelination.

EpCAM Induction Functionally Links to the Wnt-Enhanced Cell Proliferation in Human Keratinocytes

Accelerating proliferation of primary keratinocytes benefits skin autografts for severely burned patients. Wnt signal, a conserved pathway controlling cell cycle and morphogenesis in embryo, also involves in cell proliferation and tumorigenesis in adult tissues. Here the effects of Wnt signal on the growth of human interfollicular keratinocytes were investigated. We demonstrated that recombinant Wnt3a significantly promoted the growth of primary keratinocytes at a low cell density. A well-characterized GSK-3b inhibitor, BIO, activated the Wnt signals and also enhanced the colony formation of keratinocytes dose dependently. Gene expression profile of the BIO-treated keratinocytes revealed the linkage of BIO with cell mitosis and indicated that epithelial cell adhesion molecule (EpCAM), a Wnt target gene, was significantly upregulated. Compared to the sorted EpCAM^- keratinocytes, the EpCAM⁺ cells showed a higher proliferation rate and efficacy of colony formation. Inhibiting the EpCAM expression by shRNA attenuated the proliferation effect of BIO and the growth advantage of the EpCAM⁺ keratinocytes. These evidences emphasize the positive roles of canonical Wnt and EpCAM on the regulation of cell growth and self-renewal of human keratinocytes.

In utero exposure to TCDD alters Wnt signaling during mouse prostate development: linking ventral prostate agenesis to downregulated β-catenin signaling

In utero exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes ventral prostate agenesis in C57BL/6J mice by preventing ventral prostatic budding in the embryonic urogenital sinus (UGS). TCDD (5 μg/kg, po) administered to pregnant dams on embryonic day 15.5 (E15.5) activates the aryl hydrocarbon receptor in the UGS mesenchyme, disrupting the mesenchymally derived paracrine signaling that instructs epithelial prostatic budding. How TCDD alters the mesenchymal milieu is not well understood. We previously showed that TCDD disrupts some aspects of Wnt signaling in UGSs grown in vitro. Here we provide the first comprehensive, in vivo characterization of Wnt signaling in male E16.5 UGSs during normal development, and after in utero TCDD exposure. Vehicle- and TCDD-exposed UGSs were probed by in situ hybridization to assess relative abundance and localization of RNA from 46 genes that regulate Wnt signaling. TCDD altered the staining pattern of five genes, increasing staining for Wnt10a and Wnt16 and decreasing staining for Ror2, Rspo2, and Wif1. We also used immunohistochemistry to show, for the first time, activation of β-catenin (CTNNB1) signaling in ventral basal epithelium of control UGSs at E16.5. This onset of CTNNB1 signaling occurred immediately prior to the initiation of ventral prostatic budding and is characterized by a pronounced increase in CTNNB1 nuclear localization and subsequent expression of the CTNNB1 signaling target gene, Lef1. In utero TCDD exposure prevented the onset of CTNNB1 signaling and LEF1 expression in the ventral basal epithelium, thereby elucidating a likely mechanism by which TCDD contributes to failed prostatic budding in the ventral UGS.

Effect of Wnt3a on keratinocytes utilizing in vitro and bioinformatics analysis

Wingless-type (Wnt) signaling proteins participate in various cell developmental processes. A suppressive role of Wnt5a on keratinocyte growth has already been observed. However, the role of other Wnt proteins in proliferation and differentiation of keratinocytes remains unknown. Here, we investigated the effects of the Wnt ligand, Wnt3a, on proliferation and differentiation of keratinocytes. Keratinocytes from normal human skin were cultured and treated with recombinant Wnt3a alone or in combination with the inflammatory cytokine, tumor necrosis factor α (TNFα). Furthermore, using bioinformatics, we analyzed the biochemical parameters, molecular evolution, and protein–protein interaction network for the Wnt family. Application of recombinant Wnt3a showed an anti-proliferative effect on keratinocytes in a dose-dependent manner. After treatment with TNFα, Wnt3a still demonstrated an anti-proliferative effect on human keratinocytes. Exogenous treatment of Wnt3a was unable to alter mRNA expression of differentiation markers of keratinocytes, whereas an altered expression was observed in TNFα-stimulated keratinocytes. In silico phylogenetic, biochemical, and protein–protein interaction analysis showed several close relationships among the family members of the Wnt family. Moreover, a close phylogenetic and biochemical similarity was observed between Wnt3a and Wnt5a. Finally, we proposed a hypothetical mechanism to illustrate how the Wnt3a protein may inhibit the process of proliferation in keratinocytes, which would be useful for future researchers.

Wnt5a/β-catenin signaling drives calcium-induced differentiation of human primary keratinocytes

It is well established that a gradient of extracellular calcium within the epidermis regulates the differentiation of keratinocytes. However, the molecular mechanisms implicated in this process are not fully understood. RNA interference of the calcium-sensing receptor (CaSR) showed that CaSR is essential in calcium-induced differentiation of normal human epidermal keratinocytes (NHEKs) by increasing the levels of free intracellular calcium, which upregulates the expression of Wnt5a but not Wnt3a, Wnt4, and Dkk-1 in the cells. Subsequently, autocrine Wnt5a promotes the differentiation of NHEKs, determined by increased biosynthesis of keratin-1 and loricrin, whereas proliferation is suppressed. Addition of both Wnt5a and calcium to NHEKs activated the Wnt/β-catenin signaling pathway as indicated by (i) increased stability of β-catenin in the cells, (ii) enhanced β-catenin transcriptional activity, demonstrated by a luciferase-based β-catenin-activated reporter assay, and (iii) augmented Wnt/β-catenin target gene expression. NHEKs depleted for β-catenin had a significantly reduced susceptibility to calcium-induced differentiation. Knockdown of axin 2, an antagonist of β-catenin stability, enhanced the biosynthesis of keratin-1 and loricrin in the cells. Our findings establish a directional crosstalk between CaSR and Wnt/β-catenin signaling in keratinocyte differentiation via Wnt5a that acts as an autocrine stimulus in this process.

Genetic variants of the Wnt signaling pathway as predictors of recurrence and survival in early-stage non-small cell lung cancer patients

Early-stage non-small cell lung cancer (NSCLC) is potentially curative. Nevertheless, many patients will show disease recurrence after curative treatment. The Wnt signaling pathway is a developmental and stem cell pathway that plays an important role in tumorigenesis and may affect cancer progression. We hypothesize that genetic variants of the Wnt pathway may influence clinical outcome in early-stage NSCLC patients. We genotyped 441 functional and tagging single nucleotide polymorphisms (SNPs) from 54 genes of the Wnt pathway in 535 early-stage NSCLC patients treated with curative intent therapy including surgery and chemotherapy. For validation, 4 top SNPs were genotyped in 301 early-stage NSCLC patients from the Mayo Clinic. Cox proportional hazard model and combined SNP analyses were performed to identify significant SNPs correlated with recurrence-free and overall survival. Results from discovery group showed a total of 40 SNPs in 20 genes correlated with disease recurrence (P < 0.05). After correction for multiple comparisons, rs2536182 near Wnt16 remained significant (q < 0.1), which was validated in the replication population. Thirty-nine SNPs in 16 genes correlated with overall survival (P < 0.05) in the discovery group, and seven remained significant after multiple comparisons were considered (q < 0.1). In patients receiving surgery-only treatment, rs10898563 of FZD4 gene was associated with both recurrence-free and overall survival. Joint SNP analyses identified predictive markers for recurrence stratified by treatment. Our findings suggest inherited genetic variation in the Wnt signaling pathway may contribute to variable clinical outcomes for patients with early-stage NSCLC.

Wnt16 is involved in intramembranous ossification and suppresses osteoblast differentiation through the Wnt/β-catenin pathway

In the course of embryonic development skeletal elements form either through intramembranous or endochondral ossification. Wnt proteins play diverse roles during vertebrate skeletal development. Wnt16 is a key factor in developing long bones, but its exact role in craniofacial bone formation remains unclear. This study was initially undertaken to investigate the expression of Wnt16 during craniofacial bone development in mouse embryos. Wnt16 expression in the osteoid of calvaria, maxilla, and mandible started later than that of ALP and osteocalcin (OCN), but before mineralization of the craniofacial bones, suggesting that Wnt16 is involved in intramembranous ossification in the head. To confirm this, MC3T3-E1 cells were transfected with an adenovirus containing Wnt16 (Ad-Wnt16). Ad-Wnt16 cells showed decreased ALP activity and less mineralized nodule formations compared with control cells. In addition, the mRNA levels of osteogenic markers were reduced. Moreover, Wnt16 activated β-catenin signaling in MC3T3-E1 cells at both transcription and protein levels as shown by a TOPflash luciferase reporter gene assay and western blot analysis. On the other hand, Wnt/β-catenin pathway blockade by Dickkopf 1 abrogated the suppression of mineralization by Wnt16. Our findings suggest that Wnt16 is involved in intramembranous ossification and suppresses osteoblast differentiation through the Wnt/β-catenin pathway.

WNT5A encodes two isoforms with distinct functions in cancers

WNT5A, a member of the WNT family of secreted lipid-modified glycoproteins, is a critical regulator of a host of developmental processes, including limb formation, lung morphogenesis, intestinal elongation and mammary gland development. Altered WNT5A expression has been associated with a number of cancers. Interestingly, in certain types of cancers, such as hematological malignancies and colorectal carcinoma, WNT5A is inactivated and exerts a tumor suppressive function, while in other cancers, such as melanoma and gastric carcinoma, WNT5A is overexpressed and promotes tumor progression. The mechanism by which WNT5A achieves these distinct activities in cancers is poorly understood. Here, we provide evidence that the WNT5A gene produces two protein isoforms, WNT5A-long (WNT5A-L) and WNT5A-short (WNT5A-S). Amino-terminal sequencing and a WNT5A-L specific antibody demonstrate that the mature and secreted isoforms are distinct, with WNT5A-L carrying an additional 18 N-terminal amino acids. Biochemical analysis indicates that both purified proteins are similar with respect to their stability, hydrophobicity and WNT/β-catenin signaling activity. Nonetheless, modulation of these two WNT5A isoforms, either through ectopic expression or knockdown, demonstrates that they exert distinct activities in cancer cell lines: while WNT5A-L inhibits proliferation of tumor cell lines, WNT5A-S promotes their growth. Finally, we show that expression of these two WNT5A isoforms is altered in breast and cervix carcinomas, as well as in the most aggressive neuroblastoma tumors. In these cancers, WNT5A-L is frequently down-regulated, whereas WNT5A-S is found overexpressed in a significant fraction of tumors. Altogether, our study provides evidence that the distinct activities of WNT5A in cancer can be attributed to the production of two WNT5A isoforms.

Astragaloside IV Downregulates β-Catenin in Rat Keratinocytes to Counter LiCl-Induced Inhibition of Proliferation and Migration

Re-epithelialization is a crucial step towards wound healing. The traditional Chinese medicine, Astragalus membranaceus (Fisch) Bge, has been used for hundreds of years for many kinds of ulcerated wounds. Recent research has identified the active compound in this drug as astragaloside IV (AS-IV), but the underlying molecular mechanisms of its therapeutic action on keratinocytes remain poorly understood. In this study, we used an in vitro model of ulcer-like wound processes, lithium chloride (LiCl)-induced cultured mouse keratinocytes, to investigate the effects of AS-IV treatment. The effects on cell proliferation were evaluated by the MTS/PMS colorimetric assay, effects on cell migration were determined by a wound-healing scratch experiment, effects on the cell cycle were analyzed by flow cytometry, and effects on protein expression were analyzed by immunoblotting and immunofluorescence. LiCl strongly inhibited cell proliferation and migration, up-regulated β-catenin expression, and down-regulated proliferating cell nuclear antigen (PCNA) expression. AS-IV treatment attenuat the inhibition of proliferation and migration, significantly reducing the enhanced β-catenin expression, and recovering PCNA and β-tubulin expression. Thus, AS-IV mediates mouse keratinocyte proliferation and migration via regulation of the Wnt signaling pathway. Down-regulating β-catenin to increase keratinocyte migration and proliferation is one mechanism by which AS-IV can promote ulcerated wound healing.

A somitic Wnt16/Notch pathway specifies haematopoietic stem cells

Haematopoietic stem cells (HSCs) are a self-renewing population that continuously replenish all blood and immune cells during the lifetime of an individual^{1, 2}. HSCs are used clinically to treat a wide array of diseases, including acute leukaemias and congenital blood disorders, but obtaining suitable numbers of cells and finding immune compatible donors remain serious problems. These concerns have led to an interest in the conversion of embryonic stem cells or induced pluripotent stem cells into HSCs, which is not possible using current methodologies. To accomplish this goal, it is critical to understand the native mechanisms involved in specification of HSCs during embryonic development. Here we demonstrate that Wnt16 controls a novel genetic regulatory network required for HSC specification. Non-canonical signaling by Wnt16 is required for somitic expression of the Notch ligands deltaC (dlc) and deltaD (dld), and these ligands are in turn required for establishment of definitive haematopoiesis. Notch signalling downstream of Dlc/Dld is earlier than, and distinct from known cell-autonomous requirements for Notch, strongly suggesting that novel Notch-dependent relay signal(s) induce the first HSCs in parallel to other established pathways. Our results demonstrate that somite-specific gene expression is required for the production of haemogenic endothelium.

WNTs in the neonatal mouse uterus: potential regulation of endometrial gland development

The WNTs are secreted proteins that control essential developmental processes, such as embryonic patterning, cell growth, migration, and differentiation. In mice, three members of the Wnt gene family (Wnt4, Wnt5a, and Wnt7a) have been studied extensively in the female reproductive tract. The present study determined effects of postnatal day and exposure to diethylstilbestrol (DES) on Wnt and Fzd gene expression in the mouse uterus as well as the biological role of Wnt11 in postnatal mouse uterine development and function. Wnt4, Wnt5a, Wnt7a, Wnt7b, Wnt11, Wnt16, Fzd6, and Fzd10 were detected by in situ hybridization in the neonatal mouse uterus. In situ hybridization analyses revealed that Wnt4, Wnt5a, and Wnt16 were localized in the endometrial stroma, whereas Wnt7a, Wnt7b, Wnt11, Fzd6, and Fzd10 were in the uterine epithelia of neonatal mice. Exposure of mice to estrogen or estrogen receptor agonists during critical development periods inhibits endometrial adenogenesis. In the present study, DES-induced disruption of endometrial gland development was associated with reduction or suppression of Wnt4, Wnt5a, Wnt7a, Wnt11, Wnt16, and Fzd10. Ablation of Wnt11, an epithelial-expressed, DES-regulated gene, in the neonatal uterus did not affect endometrial adenogenesis or expression of other Wnt genes. Interestingly, Wnt11-deleted uteri had more endometrial glands on Postnatal Day 10. Although CTNNB1 expression was not affected by ablation of Wnt11, Vangl2 was inhibited in the uteri of Wnt11(d/d) mice. These results support the idea that a number of different Wnt genes are potential regulators for uterine morphogenesis; however, Wnt11 does not have a direct effect on uterine development.

A molecular study of desmosomes identifies a desmoglein isoform switch in head and neck squamous cell carcinoma

Desmosomes, the intercellular junctions that confer strong adhesion between epithelial cells, are frequently altered in malignancy. However, a comprehensive analysis of these structures has not been carried out in oral neoplasia. Oral squamous cell carcinomas (SCCs) and pre-malignant dysplasia can be sub-classified according to their in vitro replicative lifespan, where the immortal dysplasia (ID) and carcinoma (IC) subsets have p16(ink4a) and p53 dysfunction, telomerase deregulation and genetic instability and the mortal subset (MD and MC) do not. We found that the desmosomal proteins exhibit a distinct expression pattern in oral mucosa when compared with epidermis in vivo. Microarray data from a large panel of lines revealed that the transcript levels of DSG3, DSC2/3, DP, PG and PKP1 were reduced in ID and IC. Interestingly, DSG2 was up-regulated in MC. Reduction of DSG3 and up-regulation of DSG2 were found in two independent microarray datasets. Significantly, we demonstrated that reduction of DSG3 and up-regulation of DSG2 was reversible in vitro by using RNAi-mediated knockdown of DSG2 in IC cells. The remaining desmosomal proteins were largely disrupted or internalized and associated with retraction of keratin intermediate filaments in oral SCC lines. These findings suggest dysfunction and loss of desmosomal components are common events in the immortal class of oral SCC and that these events may precede overt malignancy.

Axial patterning in hydra

Morphogen gradients play an important role in pattern formation during early stages of embryonic development in many bilaterians. In an adult hydra, axial patterning processes are constantly active because of the tissue dynamics in the adult. These processes include an organizer region in the head, which continuously produces and transmits two signals that are distributed in gradients down the body column. One signal sets up and maintains the head activation gradient, which is a morphogenetic gradient. This gradient confers the capacity of head formation on tissue of the body column, which takes place during bud formation, hydra's mode of asexual reproduction, as well as during head regeneration following bisection of the animal anywhere along the body column. The other signal sets up the head inhibition gradient, which prevents head formation, thereby restricting bud formation to the lower part of the body column in an adult hydra. Little is known about the molecular basis of the two gradients. In contrast, the canonical Wnt pathway plays a central role in setting up and maintaining the head organizer.

Downstream targets of FOXM1: CEP55 and HELLS are cancer progression markers of head and neck squamous cell carcinoma

We recently showed that upregulation of a key oncogene FOXM1 precedes head and neck squamous cell carcinoma (HNSCC) malignancy. Furthermore, we also identified a centrosomal protein CEP55 and a DNA helicase/putative stem cell marker HELLS, which are both downstream targets of FOXM1. In this study, we have investigated the expression profiles of CEP55 and HELLS using immunohistochemistry and quantified by digital densitometry in a tissue panel (20 samples) consisting of normal oral mucosa, dysplasias, HNSCC and lymph node metastasis (LnMet) samples. Furthermore, we corroborated our findings using absolute real-time PCR (qPCR) on a panel of 12 primary normal human oral keratinocytes, five dysplasia and 10 HNSCC cell lines. Finally, we validated our study using bioinformatics microarray analysis on an independent HNSCC patient cohort (four normal and 16 tumours). In normal oral mucosa, CEP55 protein was detected at very low level within the upper differentiated layers. In contrast, CEP55 was highly expressed in oral dysplasia whereas only moderate expression was detected in HNSCC and LnMet. Low level of HELLS expression was detected in the basal cell layer of the normal oral mucosa, moderate level was seen in dysplasia and high levels in both HNSCC and LnMet. These expression patterns were consistent with both qPCR data from the cell line panel and microarray data analysis of TNM-stage defined HNSCC samples confirming the progressive expression pattern of CEP55 and HELLS. To our knowledge, this is the first pilot study demonstrating that both CEP55 and HELLS mRNA and protein expression positively correlate with pre-malignancy and HNSCC progression. This study provides strong evidence that CEP55 and HELLS may be used in conjunction with FOXM1 as a biomarker set for early cancer detection and indicators of malignant conversion and progression.